Microbiology Short Course for Parents

Microbiology is the study of "germs" or microorganisms. The two main groups of microorganisms that we are concerned about, as far as causing illnesses, are bacteria and viruses.

Bacteria are living cells-that is, they have all the genetic and internal structures that are needed to live and reproduce.

Viruses are not complete cells. They consist of some genetic material (DNA or RNA) coated with a protective covering or shell. Viruses need to enter human cells and use the "machinery" inside the human's cell to live and reproduce.

Medications have been developed to kill bacterial cells. These are known as antibiotics. The antibiotics have been made in such a way to get past the bacteria's natural barriers and kill them. Bacteria then develop some "resistances" that can counteract some of the antibiotics (if you build a better mousetrap...). It is important not to overuse antibiotics or fail to properly take antibiotics so we can avoid bacteria that develop resistance to antibiotics.

Because viruses are completely different types of microorganisms, antibiotics do not work to kill them. There are very few viruses that we have medicines for at this time (influenza and severe herpes virus infections are two exceptions). There are vaccines that prevent certain viral infections (polio, measles, mumps, rubella, chicken pox, hepatitis A and B).

The majority of acute illnesses that children get are viral in origin. The viruses eventually are managed by the immune system and the illness is over. In other words, we have to let it "run its course." Common viral infections are usually not serious but can make children feel quite ill for several days. There also are rare times that viruses do cause serious illness or complications that can be severe. There are hundreds of types of viruses. Some commonly known ones are listed below.

Parvovirus Causes Fifth Disease
Adenovirus 37 human types. Cause eye infections, cold symptoms, sore throat
Herpes Roseola, chicken pox, HSV I mouth ulcers, CMV, EBV (mono)
Picorna I subtype called Rhinovirus has at least 100 common cold strains Enteroviruses are in this group, including Coxsackie (the cause of hand, foot and mouth syndrome). Enteroviruses can cause fever without other symptoms, vomiting and diarrhea, stomach pain, cold symptoms, sore throat, eye infections and rashes.
Reovirus Rotavirus
Corona Some colds
Orthomyxo Influenza A and B
Paramyxo 3 strains of parainfluenza which can cause croup
Rhabdo Rabies

Bacterial infections that are common are things like strep throat, impetigo, urinary tract infections, some pneumonias and bronchial infections, and many ear infections. Bacterial infections often follow a viral infection, such as an ear or sinus infection following a "cold." The underlying virus will still get better on its own, but we often treat with antibiotics once a "secondary" bacterial infection occurs or is suspected. Sometimes it is difficult to tell when a virus is still the predominant cause of the illness or if a bacterial infection is beginning. Often watching for persisting or worsening symptoms is necessary to be sure. Once an antibiotic is prescribed, you should see improvement in the illness/symptoms in 48-72 hours.

There are some common misconceptions regarding infections that should be cleared up.

1) If there is fever, there is an "infection" (meaning that the illness is caused by bacteria and needs antibiotics). Both viruses and bacteria cause infections and illness, including possible fever. The presence of fever doesn't signify that an antibiotic is needed since a large number of viruses cause significant fevers.

2) Green runny nose means bacterial infection. This is not necessarily true since in the normal course of a cold the nasal mucus can be yellow or green for several days and then clear up. A continuous, prolonged period (10-21 days) of green runny nose is likely to be a bacterial infection since most runny noses from viral upper respiratory infections will have improved by that time.

3) Cold weather or wind makes the children sick. You need a microorganism to get sick! It is true that more illness occurs in the cold winter months. Part of the reason is that we are all crammed indoors spreading our germs more effectively. Part of the reason also is that certain viruses have seasonal variations and mainly occur during winter months (influenza epidemics, RSV, croup viruses, etc.).

4) It's good to "catch it early." Because most viral infections must run their course, prudent watching of signs and symptoms is the key. An office visit early in a viral illness cannot prevent the progression of the illness nor can it stave off a secondary bacterial infection. If a child has a very ill appearance, ear pain, pain with urination, continued fast breathing rate (more than 60 breaths per minute), becomes very lethargic, has fever of greater than 101 ° for 5 days, or appears dehydrated (dry mouth, infrequent urination), please call for advice or an appointment.